The rule of mixtures
Along the fibres, average the stiffness by volume (135 GPa predicted, 141 measured for AS4/8552); across, average the softness (10.7 predicted, 10 measured). Doubling the resin stiffness barely moves E1 and nearly doubles E2.
Predict · at 0:57 in the video
Now double the resin's stiffness. Does the along-fibre stiffness change much? And across?
Along, hardly at all: from 135 to about 137. Across, it nearly doubles: from 10.7 to about 21. In the chain, the resin does most of the stretching, so making it stiffer changes almost everything across, and almost nothing along.
This course is our own. These books go deeper.
- Basic Mechanics of Laminated Composite Plates, A. T. Nettles, NASA Reference Publication 1351, 1994
- Mechanics of Composite Materials, R. M. Jones, Taylor & Francis, 2nd ed., 1999
- Engineering Mechanics of Composite Materials, I. M. Daniel & O. Ishai, Oxford University Press, 2nd ed., 2006
- Design and Analysis of Composite Structures, C. Kassapoglou, Wiley, 2nd ed., 2013
- Composite Materials Handbook (CMH-17), Volume 3, Rev. G, CMH-17, SAE International, 2012
The course designs in AddPly, our browser app for laminate design: regions, ply stacks with live stacking-rule checks, thickness, mass and the ply book. It does not do strength, failure or draping; where a lesson covers those, the simulation is our own.
Simulations in this lesson are our own. Ply data come from the datasheet or textbook named on screen; where a number rests on an assumption, the video says so.
